Increased thalamic phospholipid concentration evident in bipolar I disorder

Glutamatergic and N-Acetylaspartate Metabolites in Bipolar Disorder: A Systematic Review and Meta-Analysis of Proton Magnetic Resonance Spectroscopy Studies

The exact neurobiological mechanisms of bipolar disorder (BD) remain unknown. However, some neurometabolites could be implicated, including Glutamate (Glu), Glutamine (Gln), Glx, and N-acetylaspartate (NAA). Proton Magnetic Resonance Spectroscopy (¹H-MRS) allows one to quantify these metabolites in the human brain. Thus, we conducted a systematic review and meta-analysis of the literature to compare their levels between BD patients and healthy controls (HC). The main inclusion criteria for inclusion were ¹H-MRS studies comparing levels of Glu, Gln, Glx, and NAA in the prefrontal cortex (PFC), anterior cingulate cortex (ACC), and hippocampi between patients with BD in clinical remission or a major depressive episode and HC. Thirty-three studies were included. NAA levels were significantly lower in the left white matter PFC (wmPFC) of depressive and remitted BD patients compared to controls and were also significantly higher in the left dorsolateral PFC (dlPFC) of depressive BD patients compared to HC. Gln levels were significantly higher in the ACC of remitted BD patients compared to in HC. The decreased levels of NAA of BD patients may be related to the alterations in neuroplasticity and synaptic plasticity found in BD patients and may explain the deep white matter hyperintensities frequently observed via magnetic resonance imagery.

Magnetic Resonance Spectroscopy and Bipolar Disorder: How Feasible Is This Pairing?

Bipolar disorder is a psychiatric disorder that affects a significant part of the world's population; however, its diagnosis is difficult, mainly because of the lack of biomarkers and objective tests that aid the clinical evaluation. Proton magnetic resonance spectroscopy (MRS) is a tool that is relatively unused in the medical field. Its application arises from conventional magnetic resonance, and allows non-invasive, in vivo, the study of various metabolites and compounds in the human brain. This method may allow the assessment of neurobiochemical alterations in bipolar patients. One of the main advantages of this study type is the simplicity in its use since it only needs a standard magnetic resonator. All these characteristics make it an attractive diagnostic tool that can be used anywhere, including in low-middle-income countries. In conclusion, MRS has potential as a diagnostic tool for bipolar disorder; nevertheless, using it for this purpose still requires additional steps.

Associations between executive function impairment and biochemical abnormalities in bipolar disorder with suicidal ideation

BACKGROUND

Executive dysfunction and biochemical abnormalities using proton magnetic resonance spectroscopy (¹H-MRS) have been reported in bipolar disorder (BD). Much less is known about the information from BD with suicidal ideation (SI). This study aimed to assess alterations of execution function and biochemical metabolism in BD with SI, in BD without SI, and in healthy controls. The associations between execution function and biochemical metabolism in the two BD patient groups were also been studied.

METHODS

92 patients with bipolar disorder during a depressive episode (50 with current SI, and 42 without SI), as well as, 43 healthy controls were recruited in our study. Executive function was assessed by Wisconsin Card Sorting Test (WCST). Bilateral metabolite levels of prefrontal cortex (PFC), anterior cingulated cortex (ACC), lenticular nucleus (LN) of basal ganglia and thalamus were obtained by ¹H-MRS at 3.0 T, then determined the ratios of N-acetyl aspartate (NAA), choline-containing compounds (Cho), myo-inositol (mI) to creatine (Cr).

RESULTS

Number of categories completed (CC) in BD with SI was significantly less than healthy controls. NAA/Cr ratios of left PFC in the two BD patient groups (with or without SI) were significantly lower than healthy controls, and NAA/Cr ratios of left thalamus were significantly higher than healthy controls. Moreover, NAA/Cr ratio of right LN in BD without SI was higher than BD with SI and healthy controls. For BD with SI, NAA/Cr ratio of left thalamus was negatively correlated with number of CC.

CONCLUSIONS

These results suggested that BD with or without SI may have abnormal NAA metabolism, and NAA/Cr ratio of right LN may distinguish SI from the BD patients. Further, BD with SI may have executive function impairment, which may be associated with the abnormal NAA metabolism in the left thalamus.

The impact of acute and short-term methamphetamine abstinence on brain metabolites: A proton magnetic resonance spectroscopy chemical shift imaging study

BACKGROUND

Abuse of methamphetamine (MA) is a global health concern. Previous ¹H-MRS studies have found that, with methamphetamine abstinence (MAA), there are changes in n-acetyl-aspartate (NAA/Cr), myo-inositol (mI/Cr), choline (Cho/Cr and Cho/NAA), and glutamate with glutamine (Glx) metabolites. Limited studies have investigated the effect of acute MAA, and acute-to-short-term MAA on brain metabolites.

METHODS

Adults with chronic MA dependence (n = 31) and healthy controls (n = 22) were recruited. Two-dimensional chemical shift ¹H-MRS imaging (TR2000 ms, TE30 ms) slice was performed and included voxels in bilateral anterior-cingulate (ACC), frontal-white-matter (FWM), and dorsolateral-prefrontal-cortices (DLPFC). Control participants were scanned once. The MA group was scanned twice, with acute (1.5 ± 0.6 weeks, n = 31) and short-term MAA (5.1 ± 0.8 weeks, n = 22). The change in ¹H-MRS metabolites over time (n = 19) was also investigated. Standard ¹H-MRS metabolites are reported relative to Cr + PCr.

RESULTS

Acute MAA showed lower n-acetyl-aspartate (NAA) and n-acetyl-aspartate with n-acetyl-aspartyl-glutamate (NAA + NAAG) in left DLPFC, and glycerophosphocholine with phosphocholine (GPC + PCh) in left FWM. Short-term MAA showed lower NAA + NAAG and higher myo-inositol (mI) in right ACC, lower NAA and NAA + NAAG in the left DLPFC, and lower GPC + PCh in left FWM. Over time, MAA showed decreased NAA and NAA + NAAG and increased mI in right ACC, decreased NAA and NAA + NAAG in right FWM, and decreased in mI in left FWM.

CONCLUSION

In acute MAA, there was damage to the integrity of neuronal tissue, which was enhanced with short-term MAA. From acute to short-term MAA, activation of neuroinflammatory processes are suggested. This is the first ¹H-MRS study to report the development of neuroinflammation with loss of neuronal integrity in MAA.

Analytical approaches for lipidomics and its potential applications in neuropsychiatric disorders

OBJECTIVES

In this review, the authors discuss an overview of lipidomics followed by in-depth discussion of its application to the study of human diseases, including extraction methods of lipids, analytical techniques and clinical research in neuropsychiatric disorders.

METHODS

Lipidomics is a lipid-targeted metabolomics approach aiming at the comprehensive analysis of lipids in biological systems. Recent technological advancements in mass spectrometry and chromatography have greatly enhanced the development and applications of metabolic profiling of diverse lipids in complex biological samples.

RESULTS

An effective evaluation of the clinical course of diseases requires the application of very precise diagnostic and assessment approaches as early as possible. In order to achieve this, "omics" strategies offer new opportunities for biomarker identification and/or discovery in complex diseases and may provide pathological pathways understanding for diseases beyond traditional methodologies.

CONCLUSIONS

This review highlights the importance of lipidomics for the future perspectives as a tool for biomarker identification and discovery and its clinical application.

A comparison of neurometabolites between remitted bipolar disorder and depressed bipolar disorder: A proton magnetic resonance spectroscopy study

BACKGROUND

Recent many studies found the abnormal neurometabolites in the acute bipolar disorder (BD). However, limited studies were to detect neurometabolites in remitted BD, comparison between acute and remitted BD is conductive to understand the outcome of neurometabolites. This study sought to investigate the differences in neurometabolites between remitted and depressed BD patients using proton magnetic resonance spectroscopy (¹H-MRS).

METHODS

Three subject groups were enrolled: 22 remitted BD patients, 22 depressed BD patients and 24 healthy controls. All subjects underwent ¹H-MRS to measure N-acetylaspartate (NAA), Choline (Cho), myo-Inositol (mI) and Creatine (Cr) of several bilateral areas potentially involved in BD: prefrontal whiter matter (PWM), thalamus and putamen. The neurometabolite ratios were compared among three groups. The correlations between abnormal neurometabolite ratios and clinical data were computed.

RESULTS

The lower bilateral PWM NAA/Cr ratios were found in depressed BD patients than remitted BD patients and healthy controls, no differences were found between the remitted BD patients and controls. For depressed BD patients, left PWM NAA/Cr ratios showed negative correlation with age of onset, right PWM NAA/Cr ratios showed positive correlation with duration of illness.

CONCLUSIONS

Our findings suggest the abnormal neurometabolites in the prefrontal lobe whiter may occur in the depressed BD. The remitted BD may resemble healthy subjects in terms of neurometabolites. In addition, abnormal neurometabolites in prefrontal lobe whiter may correlate with the age of onset and illness length.

Metabolic Imaging in Humans

Metabolic imaging enhances understanding of disease metabolisms and holds great potential as a measurement tool for evaluating disease prognosis and treatment effectiveness. Advancement of techniques, such as magnetic resonance spectroscopy, positron emission tomography, and mass spectrometry, allows for improved accuracy for quantification of metabolites and present unique possibilities for use in clinic. This article reviews and discusses literature reports of metabolic imaging in humans published since 2010 according to disease type, including cancer, degenerative disorders, psychiatric disorders, and others, as well as the current application of the various related techniques.

Discovery of biochemical biomarkers for aggression: A role for metabolomics in psychiatry

Human aggression encompasses a wide range of behaviors and is related to many psychiatric disorders. We introduce the different classification systems of aggression and related disorders as a basis for discussing biochemical biomarkers and then present an overview of studies in humans (published between 1990 and 2015) that reported statistically significant associations of biochemical biomarkers with aggression, DSM-IV disorders involving aggression, and their subtypes. The markers are of different types, including inflammation markers, neurotransmitters, lipoproteins, and hormones from various classes. Most studies focused on only a limited portfolio of biomarkers, frequently a specific class only. When integrating the data, it is clear that compounds from several biological pathways have been found to be associated with aggressive behavior, indicating complexity and the need for a broad approach. In the second part of the paper, using examples from the aggression literature and psychiatric metabolomics studies, we argue that a better understanding of aggression would benefit from a more holistic approach such as provided by metabolomics. © 2016 Wiley Periodicals, Inc.

Bimodal effect of lithium plasma levels on hippocampal glutamate concentrations in bipolar II depression: a pilot study

BACKGROUND

The hippocampus has been highly implicated in the pathophysiology of bipolar disorder (BD). Nevertheless, no study has longitudinally evaluated hippocampal metabolite levels in bipolar depression under treatment with lithium.

METHODS

Nineteen medication-free BD patients (78.9% treatment-naïve and 73.7% with BD type II) presenting an acute depressive episode and 17 healthy controls were studied. Patients were treated for 6 weeks with lithium in an open-label trial. N-acetyl aspartate (NAA), creatine, choline, myo-Inositol, and glutamate levels were assessed in the left hippocampus before (week 0) and after (week 6) lithium treatment using 3T proton magnetic resonance spectroscopy (1H-MRS). The metabolite concentrations were estimated using internal water as reference and voxel segmentation for partial volume correction.

RESULTS

At baseline, acutely depressed BD patients and healthy controls exhibited similar hippocampal metabolites concentrations, with no changes after 6 weeks of lithium monotherapy. A significant correlation between antidepressant efficacy and increases in NAA concentration over time was observed. Also, there was a significant positive correlation between the changes in glutamate concentrations over follow-up and plasma lithium levels at endpoint. Mixed effects model analysis revealed a bimodal effect of lithium plasma levels in hippocampal glutamate concentrations: levels of 0.2 to 0.49 mmol/L (n=9) were associated with a decrease in glutamate concentrations, whereas the subgroup of BD subjects with "standard" lithium levels (≥ 0.50 mmol/L; n = 10) showed an overall increase in glutamate concentrations over time.

CONCLUSIONS

These preliminary results suggest that lithium has a bimodal action in hippocampal glutamate concentration depending on the plasma levels.

Thalamocortical abnormalities in auditory brainstem response patterns distinguish DSM-IV bipolar disorder type I from schizophrenia

BACKGROUND

Bipolar disorder type I (BP-I) belongs to a spectrum of affective disorders that are expressed in many different ways and therefore can be difficult to distinguish from other conditions, especially unipolar depression, schizoaffective disorder, schizophrenia (SZ), but also anxiety and personality disorders. Since early diagnosis and treatment have shown to improve the long-term prognosis, complementary specific biomarkers are of great value. The auditory brainstem response (ABR) has previously been applied successfully to identify specific abnormal ABR patterns in SZ and Asperger syndrome.

METHODS

The current study investigated the early auditory processing of complex sound stimuli e.g. forward masking, in BP-I compared to SZ patients. The ABR curves of BP-I patients (n=23) and SZ patients (n=20) were analyzed in terms of peak amplitudes and correlation with an ABR norm curve based on a non-psychiatric control group (n=20).

RESULTS

BP-I patients had significantly higher wave III (p=0.0062) and wave VII (p=0.0472) amplitudes compared with SZ patients. Furthermore, BP-I patients, and to a lesser extent SZ patients, showed low correlation with the norm ABR curve in the part of the curve comprising waves VI-VII.

LIMITATIONS

Sample size was relatively small and study groups were not matched for age and gender.

CONCLUSIONS

BP-I patients showed specific aberrances, specifically in the latter part of the ABR curve, implicating abnormalities in thalamocortical circuitry. The abnormal ABR wave patterns significantly separated BP-I patients from SZ patients suggesting that ABR might serve as a biomarker for BP-I.

Targeting mitochondrially mediated plasticity to develop improved therapeutics for bipolar disorder

INTRODUCTION

Bipolar disorder (BPD) is a severe illness with few treatments available. Understanding BPD pathophysiology and identifying potential relevant targets could prove useful for developing new treatments. Remarkably, subtle impairments of mitochondrial function may play an important role in BPD pathophysiology.

AREAS COVERED

This article focuses on human studies and reviews evidence of mitochondrial dysfunction in BPD as a promising target for the development of new, improved treatments. Mitochondria are crucial for energy production, generated mainly through the electron transport chain (ETC) and play an important role in regulating apoptosis and calcium (Ca²⁺) signaling as well as synaptic plasticity. Mitochondria move throughout the neurons to provide energy for intracellular signaling. Studies showed polymorphisms of mitochondria-related genes as risk factors for BPD. Postmortem studies in BPD also show decreased ETC activity/expression and increased nitrosative and oxidative stress (OxS) in patient brains. BPD has been also associated with increased OxS, Ca²⁺ dysregulation and increased proapoptotic signaling in peripheral blood. Neuroimaging studies consistently show decreased energy levels and pH in brains of BPD patients.

EXPERT OPINION

Targeting mitochondrial function, and their role in energy metabolism, synaptic plasticity and cell survival, may be an important avenue for development of new mood-stabilizing agents.